Slideshow: The stages of puberty

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Puberty: It's not one size fits all

Puberty starts when the brain triggers the production of sex hormones. Although physical changes follow a predictable pattern every child develops at his or her own pace. Girls develop more quickly than boys. For most girls, puberty begins around age 8-14 years old (average age is 11). For boys, puberty starts from 9-14 years of age (average age is 12).

Budding breasts can signal puberty

Breast growth is usually the first sign of puberty that girls will notice. First, small lumps form behind the nipples. They can be sore but the pain goes away as breasts grow and change shape over the next few years. As they grow, it's not unusual for one breast to develop more slowly than the other. Boys may also have some swelling on their chest but it tends to go away within a year or two.

Boys: Genital changes

The first sign of puberty in boys is subtle -- an increase in testicle size. About a year later the penis and scrotum start to grow. During this time semen can be released during an erection when a boy is awake or when he is asleep.

Hair growth in puberty

After breasts and testicles start growing, body hair will start to grow and become thicker. For both boys and girls new hair will start growing under the armpits and in the pubic area around the genitals. Arm and leg hair gets thicker. Boys may also start developing chest and facial hair.

Spots: An early sign of puberty

Mild acne may be normal in early puberty. The high hormone levels of puberty can alter acid levels in the skin, encouraging bacteria and triggering acne outbreaks. The oil glands are more active and your child will probably sweat more. Keeping the face and body clean can help but if acne is a concern talk to your GP who may, in some cases, recommend antibacterial cream or tablets.

Later stages of puberty for girls

About a year after puberty begins girls experience a growth spurt. A girl will get taller and start to get wider hips and fuller breasts. Some curve-related fat will appear on her stomach, bottom and legs. Girls usually reach adult height by their mid to late teens.

Growth spurts: From boys to men

The peak growth spurt for boys happens later than it does for girls. It happens around six months after pubic hair development. When it does, your son's shoulders will become fuller and broader and he'll also grow taller. His face shape will look less round and more adult-like. Depending on when puberty starts, he may not reach his adult height until his late teens or even early 20s.

The first period: Puberty's ending

A girl usually starts her first period between 10 and 16 years old (about two to two and a half years after she starts puberty). Menstruation is a sign that she's physically an adult and is able to get pregnant. You may want to talk to your GP if your daughter doesn't get her first period by the time she's 16.

Puberty: Voice breaking

Towards the end of puberty your son's voice may start changing. This is normal and will be complete after a few months when his voice will permanently sound deeper. Voice changes are caused by testosterone, a hormone released in boys during puberty. It causes the vocal cords to get thicker and longer and his larynx to grow bigger.

Growing up too fast: Early puberty

Some children become sexually mature at a very early age. Early, or precocious, puberty is when a child shows symptoms of puberty -- such as breast development, enlargement of the testes and pubic hair growth -- before age six - eight in girls or nine in boys. Early puberty is linked with weak bones in later life and growing up particularly short. In rare cases early puberty is due to hormone exposure or a problem with the thyroid, ovaries or brain. Talk to your GP if you're concerned.

When to seek medical advice

Keep track of your child's bodily changes in a way that respects his or her desire for privacy. Seek medical advice if:

Puberty signs appear before age six–eight in girls or in a boy before age nine.

Puberty changes don't appear in a girl by age 13 or in a boy by age 14

THIS TOOL DOES NOT PROVIDE MEDICAL ADVICE. It is intended for general information purposes only and does not address individual circumstances. It is not a substitute for professional medical advice, diagnosis or treatment and should not be relied on to make decisions about your health. Never ignore professional medical advice in seeking treatment because of something you have read on the BootsWebMD Site. If you have a medical problem please contact your GP. In England call 111. In Scotland call NHS 24. In Wales, call NHS Direct Wales. In the case of medical emergencies, always dial 999.

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